Solid-state reference electrodes based on carbon nanotubes and polyacrylate membranes

A novel potentiometric solid-state reference electrode containing single-walled carbon nanotubes as the transducer layer between a polyacrylate membrane and the conductor is reported here. Single-walled carbon nanotubes act as an efficient transducer of the constant potentiometric signal originating from the reference membrane containing the Ag/AgCl/Cl− ions system, and they are needed to obtain a stable reference potentiometric signal. Furthermore, we have taken advantage of the light insensitivity of single-walled carbon nanotubes to improve the analytical performance characteristics of previously reported solid-state reference electrodes. Four different polyacrylate polymers have been selected in order to identify the most efficient reservoir for the Ag/AgCl system. Finally, two different arrangements have been assessed: (1) a solid-state reference electrode using photo-polymerised n-butyl acrylate polymer and (2) a thermo-polymerised methyl methacrylate:n-butyl acrylate (1:10) polymer. The sensitivity to various salts, pH and light, as well as time of response and stability, has been tested: the best results were obtained using single-walled carbon nanotubes and photo-polymerised n-butyl acrylate polymer. Water transport plays an important role in the potentiometric performance of acrylate membranes, so a new screening test method has been developed to qualitatively assess the difference in water percolation between the polyacrylic membranes studied. The results presented here open the way for the true miniaturisation of potentiometric systems using the excellent properties of single-walled carbon nanotubes

Design and synthesis of porous ZnTiO<inf>3</inf>/TiO<inf>2</inf> nanocages with heterojunctions for enhanced photocatalytic H<inf>2</inf> production

Despite the tremendous potential applications of hollow micro/nanostructures, their composition has been limited to mainly single chemical compounds. Inspired by recent innovations in the areas of metal organic frameworks (MOFs) and nanocoating, here, we report the rational synthesis of mesoporous ZnTiO3/TiO2 hollow polyhedra (MZTHP) obtained by hydrothermal treatment of zeolitic imidazolate framework-8 (ZIF-8)@TiO2 core-shell polyhedral particles. The subsequent calcination of these particles caused phase transformation from TiO2 to ZnTiO3 and eventually induced the formation of Zn2TiO4. In addition, the fabrication of these hollow structures revealed a way for the preparation of hollow polyhedral photocatalysts with Pt nanoparticles deposited onto their external surface (PHS-1) or encapsulated inside their hollow structures (PHS-2). Importantly, these two types of Pt-decorated nanoparticles are shown to exhibit an improved yet distinctly different performance for photocatalytic hydrogen production, highlighting that the photocatalytic activity correlates with the Pt location and dispersion

A holistic analysis of surface, chemical bonding states and mechanical properties of sol-gel synthesized CoZn-oxide coatings complemented by finite element modeling

This article presents a comprehensive study on surface chemical bonding states, morphological features, mechanical properties, finite element modeling, and water contact angle measurements of wet chemical based dip-coated CoZn-oxide thin film coatings. Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Nanoindentation, finite element method (FEM) modeling, and drop shape analysis techniques were used to carry out the detailed measurements. AFM studies showed that the surface roughness values of all the coatings sturdily increased with the increase in sol concentrations. The gradual increase in sol concentrations and annealing temperature also had a remarkable influence over the Co, and Zn-contents of these coatings given by XPS analysis. The deconvolution of Co 2p3/2 photoelectron lines revealed the formation of Co(OH)2, CoO, Co2O3, and Co3O4 phases from the coatings surface while low intensity satellite peaks developed due to a partial spinel lattice structure of Co-ions. The occurrence of Co3O4, CoO, and ZnO phases were also confirmed from the deconvolution of O 1s photoelectron lines. The elastic modulus, E, of CoZn-oxide thin film coating, varied within the range of 43.7–69.2 GPa was comparable with that in CoCuO thin film coatings. The maximum stress level induced was estimated to be in the range of 4.0–6.5 GPa. However, as the thickness of the coatings is increased, the maximum stress level slightly decreased. The coatings were moderately hydrophobic

Hierarchically porous cobalt-carbon nanosphere-in-microsphere composites with tunable properties for catalytic pollutant degradation and electrochemical energy storage

Unreliable energy supply and environmental pollution are two major concerns of the human society in this century. Herein, we report a rational approach on preparation of hierarchically-structured cobalt-carbon composites with tunable properties for a number of applications. A facile hydrothermal treatment of cobalt nitrate and sucrose results in the formation of a metallic cobalt-amorphous carbon composite with cobalt nanospheres anchored homogenously on an amorphous carbon substrate. Tuning the calcination conditions in air will generate either a metallic cobalt-cobalt oxide core-shell structure with magnetism or a fully oxidized Co3O4 composite. The different materials are demonstrated as anodes for lithium-ion batteries (LIBs) and catalysts for advanced oxidation-based wastewater remediation. A fully oxidized composite (FC@CS, fully oxidized Co loaded on carbon spheres) as a LIB anode exhibits superior electrochemical performance, possessing a high reversible capacity, high initial columbic efficiency, outstanding cycling performance and excellent rate capability. The anode performance is superior to most reported Co3O4-based electrodes. Meanwhile, the partially oxidized composite (PC@CS, partially oxidized Co loaded on carbon spheres) functions as an efficient and stable catalyst for removal of phenol via peroxymonosulfate (PMS) activation, which is demonstrated via electron paramagnetic resonance (EPR) and quenching experiments for generation of radicals. More importantly, the recycled PC@CS can be further applied as a LIBs anode after full oxidation regeneration, performing comparably to FC@CS. This FC@CS → PC@CS → FC@CS transformation provides an innovative approach for efficient material synthesis, recycling and application